Section 01 of 20
Introduction
Semimembranosus is the deepest and most medial of the three hamstring muscles. Its name comes from the wide, flat, membrane-like tendon that covers the upper part of the muscle before the fleshy belly begins lower down the thigh.
It lies deep to semitendinosus on the inner back of the thigh and, together with biceps femoris and semitendinosus, forms the hamstring group that crosses both the hip and the knee. Its lower tendon fans out into several attachments around the back and inner side of the knee, forming the oblique popliteal ligament and reinforcing the knee capsule.
Section 02 of 20
Origin
| Origin | The ischial tuberosity (upper and lateral facet), by the broad membranous tendon. |
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An anatomical image for this section will be added when verified source media becomes available.
Section 03 of 20
Insertion
| Insertion | Mainly the posteromedial part of the medial condyle of the tibia, with additional slips forming the oblique popliteal ligament of the knee and reinforcing the knee joint capsule. |
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An anatomical image for this section will be added when verified source media becomes available.
Section 04 of 20
Actions
| Primary action | Hip extension and knee flexion. |
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| Secondary actions | Medial rotation of the flexed knee and pelvic and knee stabilization. |
| Movement at the joint | Hip joint and knee joint. |
| Heads / fiber groups | Single muscle with a broad flat tendon. |
| Functional examples | Walking and running (driving the leg back); climbing stairs; decelerating a kick; bending forward at the hips. |
Hip extension
Extends the thigh at the hip, as in driving the leg backward when walking or running.
Knee flexion
Bends the knee.
Medial rotation of the flexed knee
With the knee bent, helps rotate the lower leg inward.
Pelvic and knee stability
Helps control forward tilting of the pelvis and stabilizes the back of the knee.
Section 05 of 20
Nerve Innervation
| Nerve | Tibial division of the sciatic nerve, roots L5–S2. |
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The sciatic nerve runs beneath the hamstrings for most of the thigh. Pain that shoots down the back of the leg, or numbness and tingling in the leg or foot, may reflect nerve or disc involvement, not only muscle tightness.
Section 06 of 20
Blood Supply
| Blood | Perforating branches of the profunda femoris (deep femoral) artery, with the inferior gluteal artery supplying the upper part. |
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Section 07 of 20
Pictures and Visual Anatomy
An anatomical image for this section will be added when verified source media becomes available.
Section 08 of 20
Functional Movement
Semimembranosus is active in walking, running, climbing stairs, decelerating the leg during a kick, and bending forward from the hips, as in touching the toes with the knees softly bent. It helps control the speed of the swinging leg just before the foot lands.
Section 09 of 20
Synergists and Antagonists
Synergists: semitendinosus and biceps femoris (hip extension and knee flexion), and gluteus maximus (hip extension). Antagonists: the quadriceps (knee extension) and iliopsoas and rectus femoris (hip flexion).
Section 10 of 20
Palpation and Location
Client position and technique
Position the client prone with the knee slightly bent and supported. Locate the ischial tuberosity, then follow the medial hamstring mass down the inner back of the thigh. Semimembranosus lies deep to the more superficial, cord-like semitendinosus tendon; ask the client to bend the knee against light resistance to feel both tighten, and note the broader, flatter feel of semimembranosus compared with the rounder semitendinosus tendon.
Protect nearby structures
The sciatic nerve runs through the middle of the back of the thigh, and the popliteal artery, vein, and tibial nerve lie behind the knee. Avoid deep or sustained pressure directly behind the knee, use moderate pressure over the muscle belly, and stop if the client reports tingling, numbness, or sharp pain down the leg.
Section 11 of 20
Massage Therapy Relevance
The hamstrings, including semimembranosus, are commonly tight or strained in runners, sprinters, and people who sit for long periods. Hamstring and knee symptoms have many possible causes, so careful assessment matters.
Section 12 of 20
Dysfunction: What Happens When Movement Goes Wrong
Changes in how a muscle works can change how a joint moves. The points below describe possibilities that may be associated with altered muscle function; they are not diagnoses, and one muscle is never assumed to be the sole cause of a problem.
When the muscle is weak
Weakness may reduce hip extension and knee flexion strength and may be associated with more work by the other hamstrings and gluteus maximus.
When it is tight or shortened
Tightness may be associated with limited hip flexion with the knee straight and a pulling sensation in the back of the thigh.
When it is overused
Repeated sprinting, kicking, and deceleration may overload the muscle and tendon and may contribute to posterior thigh or buttock pain.
When it is strained
A strain may cause sudden pain in the back of the thigh with sprinting or overstretching; sciatica and hip problems can look similar.
When it is inhibited or others compensate
Reduced activation may be associated with reduced control of knee flexion and more load on the knee ligaments.
When it does not coordinate well with synergists and antagonists
Poor coordination with the other hamstrings and gluteus maximus may alter hip and knee control and may be associated with hamstring or knee symptoms.
Section 13 of 20
Conditions, Pathologies, and Pain Relationships
Hamstring strain
Sprinting, sudden deceleration, and overstretching (such as forceful kicking) can strain semimembranosus, causing pain in the back of the thigh, sometimes with bruising.
Proximal hamstring tendinopathy
Overload of the tendon at the ischial tuberosity may cause deep buttock pain that is worse when sitting or during hip flexion with the knee straight.
Medial knee pain
Because part of the tendon reinforces the back and inner knee, tightness or injury may be associated with posteromedial knee discomfort.
Differential considerations
Sciatica, lumbar disc problems, hip joint disease, and medial meniscus or ligament injury of the knee can all cause pain in this region.
Section 14 of 20
Example Clinical Relationship
A sprinter reports sudden pain in the inner back of the thigh during a race, with mild bruising the next day. Semimembranosus may be involved, and the pattern may be associated with a hamstring strain, but sciatica and hip problems can look similar. Gentle work on the surrounding tissue may support comfort once assessed, while a sudden pop with a palpable gap or inability to bear weight needs referral.
Section 15 of 20
Massage and Treatment Approaches
For healthy, non-acute tissue, position the client prone with the knee slightly bent and supported. Begin with broad effleurage from the knee toward the buttock, then use gentle kneading and slow longitudinal strokes along the medial hamstring mass, avoiding direct pressure behind the knee.
| Movement | Use gentle passive knee extension and hip flexion stretches within comfort; do not force range or bounce. |
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| Regional work | Consider semitendinosus, biceps femoris, gluteus maximus, gastrocnemius, and the adductors when assessment supports it. |
| Avoid | Deep pressure directly behind the knee, over an acute strain, near the ischial tuberosity if tender, or at any point that reproduces leg tingling. |
Section 16 of 20
Precautions and Contraindications
Precautions and contraindications
- Acute strain, suspected tear, or recent thigh or knee injury or surgery.
- Use caution with anticoagulant use, easy bruising, or varicose veins.
- Avoid deep pressure over the popliteal fossa (back of the knee).
- Stop if pressure causes sharp pain, numbness, or tingling down the leg.
Section 17 of 20
Red Flags and When to Refer
Red flags and referral
- Sudden severe thigh pain with a pop, bruising, and a palpable gap, or inability to bear weight (possible tear or avulsion).
- A swollen, warm, red, or painful calf or leg, especially on one side (possible blood clot).
- Numbness in the saddle area or bladder or bowel changes with back or leg pain.
- Progressive leg weakness, or thigh pain with fever or unexplained weight loss.
Section 18 of 20
Study Summary
Attachments
Origin: ischial tuberosity. Insertion: posteromedial tibial condyle and the knee capsule/oblique popliteal ligament.
Actions
Hip extension and knee flexion, with medial rotation of the flexed knee.
Supply
Tibial division of the sciatic nerve (L5–S2); perforating branches of the profunda femoris artery.
Section 19 of 20
Instructor Narration
Open narration transcript
Semimembranosus is the deepest and most medial hamstring, named for its broad, membrane-like upper tendon.
It arises from the ischial tuberosity and inserts mainly on the posteromedial tibial condyle, with slips that reinforce the back and inner side of the knee.
It extends the hip and flexes the knee, and helps rotate the bent knee inward. Semitendinosus and biceps femoris help it, and the quadriceps and hip flexors oppose it.
The tibial division of the sciatic nerve supplies it, from L5 to S2, and perforating branches of the profunda femoris artery provide its blood.
Palpate with the client prone, follow the medial hamstring mass from the ischial tuberosity down the thigh, and feel its broader, flatter texture compared with semitendinosus. Avoid deep pressure directly behind the knee.
Hamstring strain, proximal tendinopathy, and medial knee discomfort are common, and sciatica, disc, and knee joint problems can overlap. Refer a sudden pop with bruising and a gap, a swollen warm leg, saddle numbness, or progressive leg weakness.
Remember: ischial tuberosity to the posteromedial tibia; hip extension and knee flexion; tibial division of the sciatic nerve.
Section 20 of 20